Officers thought they were about to watch a drug deal go down, but ended up making a human smuggling bust instead.

Seven illegal immigrants were found in the back cab of an 18-wheeler Tuesday night at a truck stop off IH-35 South and Somerset. Investigators believe the illegal immigrants had been in the cab for more than 10 hours.

It all started when police followed a black pickup truck to the Shell Station at IH-35 and Somerset, and parked next to the 18-wheeler. Police thought there was a drug deal going on.

"They were flashing with the flashlights all the way around the truck to find out what was inside," explained a witness.

That's when they found the illegal immigrants. The big rig's driver took off running, but then turned around.

"In our experience, I would have never expected the driver to come back to the scene, much less to try to take the truck or take the truck away," said Special Agent in Charge Jerry Robinette of Immigration and Customs Enforcement.

The driver, Frank Harrington, didn't want to say much, only that he didn't know how five men and two women were found stuffed in the back cab of his truck.

"They had to do it here," Harrington told News 4. "Because it wasn't in when I stopped."

Harrington now faces federal smuggling charges.

"Whoever is responsible, they, they need to be the ones sitting here instead of me," Harrington added.

I.C.E. agents said the truck cab was air conditioned. They also said the cab was unlocked, and the illegal immigrants were free to leave at anytime.